- What did Pioneer 10 discover about Jupiter's radiation belts, and how did that damage the spacecraft?
Outer Planets and Moons Exploration
Missions to Jupiter, Saturn, Uranus, Neptune, and their moons.
- How did Pioneer 11 use Jupiter's gravity to redirect itself toward Saturn?
- What did Pioneer 11 discover during its 1979 flyby of Saturn?
- How close did Pioneer 11 come to Saturn during its closest approach, and what path did it take?
- How did astronomers use a stellar occultation to detect rings around Uranus that no one had ever seen directly?
- Why did the star's light blink out multiple times both before and after Uranus passed in front of it?
- What did Voyager 2's 1986 flyby add to the initial 1977 count of Uranus's rings and moons?
- What made the 1977 planetary alignment of Jupiter, Saturn, Uranus, and Neptune so rare, and how did it enable the Voyager missions?
- How did Voyager 1, launched after Voyager 2, end up overtaking its twin within months?
- What was included on the golden records carried by the Voyager spacecraft, and who were they meant for?
- How far has Voyager 1 traveled, and how long does its signal now take to reach Earth?
- How did James Christy spot Charon as a mere elongation on photographic plates of Pluto?
- What does it mean for Pluto and Charon to be tidally locked in a mutual gravitational stare?
- How did the discovery of Charon contribute to Pluto's 2006 reclassification as a dwarf planet?
- How did Linda Morabito come to spot Io's volcanic plume while checking navigation images?
- How many simultaneous eruptions did the imaging team eventually count on Io?
- What makes Io the most volcanically active body in the solar system?
- What else did Voyager 1 discover in the Jovian system besides Io's volcanoes?
- What changed on Io's surface between the Voyager 1 and Voyager 2 flybys four months apart?
- How many images did Voyager 2 return of the Jovian system, and what did they reveal about the Galilean moons?
- Why did the changing plumes on Io matter scientifically beyond just confirming volcanism?
- How did Voyager 1's images of Saturn's rings during its 1980 flyby overturn the textbook picture of a few smooth, broad ring bands?
- What caused the F ring to appear twisted into a helix, and what moons were discovered because of that effect?
- How many new moons of Saturn did Voyager 1 discover during its November 1980 flyby?
- What unexpected structures did Voyager 2 find in Saturn's rings that existing ring dynamics couldn't explain?
- What are the 'spokes' seen in Saturn's rings, and why do they rotate with the planet's magnetic field?
- What did Voyager 2's images of Enceladus suggest about its geological activity?
- How did Voyager 2 use Saturn's gravity to redirect itself toward Uranus, and why was the timing so rare?
- What did Voyager 2 discover about Uranus's moons and rings during its 1986 flyby?
- Why is Uranus's magnetic field, tilted 60 degrees from its rotation axis and offset from its center, so hard to explain?
- Why does Uranus roll on its side with a rotation axis tilted 98 degrees to the ecliptic?
- How did Voyager 2 send data back to Earth across 2.7 billion kilometres on such a faint radio signal?
- How did Voyager 2 use gravitational slingshots from Jupiter, Saturn, and Uranus to reach Neptune in 1989?
- What was the Great Dark Spot on Neptune, and why had it disappeared by the time Hubble looked in 1994?
- Why was it surprising to find active nitrogen geysers on Triton, a moon with a surface around -235 degrees Celsius?
- Where is Voyager 2 now, and what is it still transmitting from interstellar space?
- How close did the Galileo spacecraft come to asteroid Gaspra, and why was the flyby significant?
- How large were the scars left in Jupiter's atmosphere by the impacts, and how were they visible from Earth?
- How was Charon originally discovered in 1978, given how hard it was to see separately from Pluto?
- How did the failure of Galileo's main antenna change the mission's data-return strategy?
- What did the atmospheric probe find about Jupiter's winds and water content during its 57-minute descent?
- What evidence did the Galileo orbiter find for a liquid water ocean beneath Europa's ice?
- What roles did Carl Sagan hold in the Voyager missions and the Planetary Society during his career?
- Why did Sagan specifically request the Voyager photograph that became known as the Pale Blue Dot?
- Why couldn't engineers on Earth intervene during Cassini's orbit insertion burn at Saturn?
- What did the Huygens probe discover after separating from Cassini and descending through Titan's atmosphere?
- What did Cassini discover on Enceladus that made it a candidate for hosting life?
- What features did Huygens photograph during its descent that suggested flowing liquid on Titan?
- What liquid carves Titan's drainage channels, and at what surface temperature does it flow?
- What did Huygens find at its landing site that resembled river stones on Earth?
- Why is Titan considered the most Earth-like body in the solar system despite its alien chemistry?
- What did the Cassini spacecraft discover erupting from Enceladus's south pole?
- What evidence suggests Enceladus hides a liquid water ocean beneath its icy shell?
- Why did Enceladus's smooth young surface first puzzle scientists observing it with Voyager 2?
- Why has Enceladus become a priority target in the search for extraterrestrial life?
- What discoveries did Galileo publish in the Sidereus Nuncius about Jupiter's moons and the Moon's surface?
- What rare planetary alignment made Voyager 1's grand tour of the outer planets possible?
- How long does it take a signal from Voyager 1 to reach Earth, and what does that reveal about its distance?
- Why did Juno's orbit-insertion burn have to be performed autonomously rather than by real-time commands from Earth?
- How does Juno's titanium vault protect its electronics from Jupiter's radiation belts?
- What did Juno reveal about Jupiter's interior structure and magnetic field that surprised scientists?
- What did Cassini discover at Enceladus that made it a compelling candidate for extraterrestrial life?
- Why did Cassini's controllers choose to dive it into Saturn rather than leave it in orbit?
- What were the Grand Finale orbits, and what data did they let Cassini collect for the first time?
- What did Cassini's final telemetry show about the spacecraft as it broke apart in Saturn's atmosphere?
- What made the UAE's Hope orbiter mission historically significant?
- How far is Voyager 1 from Earth, and how long does a radio signal take to reach it and return?
- What caused Voyager 1's telemetry to become garbled starting in late 2023?
- How did JPL engineers write and transmit a software patch to fix a spacecraft 24 billion kilometres away?
- Why is it notable that Voyager 1 was still functioning and repairable while in interstellar space, decades after launch?